Description of a new species from eastern Guangxi within the Oreonectes polystigmus complex (Cypriniformes, Nemacheilidae) by integrating morphological and genetic evidence

We describe Oreonectes guidongensis sp. nov. , a new species collected from Hezhou City, Guangxi Zhuang Autonomous Region, China. Morphologically, it is distinguished from all congeners by the following combination of characters: six branched pelvic-fin rays; seven branched dorsal-fin rays; tip of pelvic fin not reaching the anus; a well-developed posterior chamber of the air bladder; 14–16 branched caudal-fin rays; 10 inner gill rakers on the first gill arch; and a distance between the posterior base of the pectoral fin and the anterior base of the pelvic fin of 18.8–27.9% of standard length. Phylogenetic analysis based on the mitochondrial cytochrome b gene supports the distinctiveness of this species, revealing genetic distances of 5.4–8.5% from its congeners. The discovery of Oreonectes guidongensis sp. nov. underscores the need to re-evaluate O. polystigmus as a potential species complex to better understand the genus’s biodiversity.